5
Carbon dioxide will not spray transfer;
therefore, the arc performance is restricted to short circuiting and
globular transfer. The advantage of
CO2 is fast welding speeds and deep penetration.
The major drawbacks of
CO, are a harsh globular transfer and high weld spatter levels. The weld surface
resulting from pure CO2
shielding is usually heavily oxidized.
A welding wire having higher amounts of deoxidizing elements is
sometimes needed to compensate for the
reactive nature of the gas. Overall, good mechanical properties
can be achieved with CO2.
Argon is often mixed with CO2 to off-set pure
CO2 performance characteristics. If
impact properties have to be maximized,
a CO2 + argon mixture is recommended.
Helium Helium
is an inert gas which is used on weld applications requiring higher heat input
for improved bead wetting,
deeper penetration and higher travel speed. In GMAW it does not produce as stable
an arc as argon.
Compared to argon, helium has a higher thermal conductivity and voltage gradient
and yields a Continued
on next page... Figure
4-2 – Comparison of Ar-5% O2 and CO2
Shielding Gas
